Scaled image anti alias

Hey guys.

Ive searched for the problem i have here on these forums but without result. Maybe it has already been discussed before, if so, please reply a link.

Anyways, my problem is, when scaling an image down (lets say 800×600) dynamicly to like 50 percent its getting very edgy. Is there a posibilaty to like anti alias the pic so it looks smooth?

In here the pictures dont get edgy because they cant scale down that much because of the table “boundries”. but it doesnt seem the picture gets edgy/blurry when you scale it bigger.

So does one of you know if its possible to make a picture anti aliased when scaling down or is that just impossible?